Problem: Tiffany did 8 more sit-ups than Emily at night. Emily did 4 sit-ups. How many sit-ups did Tiffany do?
Answer: Emily did 4 sit-ups, and Tiffany did 8 more than that, so find the sum. The sum is $4 + 8$ sit-ups. She did $4 + 8 = 12$ sit-ups.